PHAGOCYTOSIS 335 



spleen, lymph nodes, and bone marrow of animals all of them organs 

 in which large collections of leucocytic elements are found. Metch- 

 nikoff's opinions as to the leucocytic origin of the complement, or 

 "cytase," have found support in the experiments of Levaditi, 6 who 

 was able to demonstrate the absence of complement in blood plasma, 

 i.e., where no destruction of leucocytes had taken place and in those 

 of Cantacuzene, 7 who showed that cholera-immune guinea-pigs would 

 succumb to intraperitoneal injection of these bacteria when the 

 diapedesis of leucocytes had been prevented by the administration of 

 opium. 



The chapter of phagocytosis in its relation to bacterial immunity is 

 by no means closed. The problems involved in it are intricate and 

 will require much further study. The subsequent sections upon 

 opsonins, aggressins, and upon leucocyte extract, incorporate the more 

 recent studies which may be said to have followed logically in the 

 footsteps of Metchnikoff's work. 



6 Levaditi, Presse med., 1900. 



T Cantacuzcne, Ann. de 1'inst. Pasteur, 1897. 



